Adaptive underwater camera

ABSTRACT

The present invention is an underwater camera which, because of its narrow field of view, looks only at the illuminated portion of an object. The camera includes a servosystem by means of which the camera is continuously positioned to follow the illuminated portion of the object.

United States Patent Winslow 1 Mar. 7, 1972 54] ADAPTIVE UNDERWATERCAMERA [56] References Cited [72} inventor: John S. Winslow, Altadena,Calif. UNITED STATES PATENTS [73] Assignee: Tetra Tech Inc., Pasadena,Calif. 3,139,015 6/ 1964 Crockwell, ..95/17 2 Filed: A PrimaryExaminer-John M. Horan Y A Attorney-Allen E. Botney [21] Appl.No.:836,329

[ ABSTRACT 52 U.S.Cl ..95/ll,95/l6 The Present invention is anunderwater camera which [51] Int Cl Gosh 17/08 because of its narrowfield of view, looks only at the illu- [58] minated portion of anobject. The camera includes a ser- Fi'eld ofSearch ..95/12.5,ll,15,16,l7

vosystem by means of which the camera is continuously positioned tofollow the illuminated portion of the object.

6 Claims, 4 Drawing Figures "PATENTEDMAR H912- 3,648,863

sum 1 or 4 I //v VENTO/Q JOHN S. Irv/N54 OW By 0M3. W Arromv y 1ADAPTIVE UNDERWATER CAMERA The present invention relates to cameras ingeneral, and more particularly relates to cameras adapted for underwaterphotography.

It is considered by those skilled in the art that volume scanning is thebest means for photographing objects in turbid water with a satisfactorydegree of quality. By way of explanation, in volume scanning a narrowbeam of light is swept across the object while a camera with acorrespondingly narrow field of view looks only at the illuminatedportion of the object and thereby avoids seeing much of thebackscattered light from the turbid water.

It is, therefore, an object of the present invention to provide a camerafor underwater photography.

It is another object of the present invention to provide a camera thatphotographs by the technique of volume scanning.

It is a further object of the present invention to provide a panoramiccamera for underwater use whose field of view is servoed to follow thebeam reflected by the object.

It is an additional object of the present invention to provide avolume-scanning type of underwater camera with which the operator neednot estimate the range of the object.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objects and the advantages thereof, will be betterunderstood from the following description considered in connection withthe accompanying drawings in which an embodiment of the invention isillustrated by way of example. It is to be expressly understood,however, that the drawings are for the purpose of illustration anddescription only and are not intended as a definition of the limits ofthe invention.

FIG. 1 illustrates the genera] principals of an imaging system thatincorporates a camera according to the present invention;

FIG. 2A is a top view of a preferred embodiment of a camera according tothe present invention;

FIG. 2B is a side view of the camera illustrated in FIG. 2A; and

FIG. 3 is a schematic circuit diagram of a servosystem for the camerashown in FIGS. 2 A and 2 B.

For a consideration of the invention in detail, reference is now made toFIG. 1 of the drawings wherein a volumescanning-imaging system that ispositioned underwater is shown to include a fan beam light source and acamera 11 spaced from the light source by some distance D. Brieflystated, light source 10 directs its beam, designated 10a, toward somedistant object to be photographed and the beam of light reflectedtherefrom, designated 11a, is received by the camera. In order tosuitably scan the object with the light, beam 10a is rotated at aconstant angular velocity and, therefore, in accordance with the camerasmode of operation, the camera's field of view is rotated at the sameconstant angular velocity. It will be recognized that such anarrangement can image a wide object by synchronizing the motion of thelight source and the camera to make a series of strip images of angularwidth beta, beta being the beam angle. Since a certain amount ofscattering of light will take place, the angle beta is made quitenarrow, for example about 4 to reduce the quantity of backscatteredillumination viewed by the camera in relation to the desired reflectionfrom the object being viewed. For purposes of simplicity in illustratingand explaining g the basic principles involved, the reflecting object 12is shown to be circular in its configuration, with the result that thesuccessive scattering volumes are hatched triangles 13 as shown in thefigure.

Considering now the camera itself, reference is made to FIGS. 1 A and 1B wherein the camera is shown to include a watertight housing structureor case 14 that is a hollow cylindrically shaped structure open at oneend and closed at the other end. The open end of structure 14 isenclosed with a hemispherically shaped dome 15 that is made with atransparent material, such as glass, plastic, or the like, of opticalquality. The casing 14, on the other hand, may be made of metal or someother opaque material that is sturdy. Mounted within the casing is ablock or wall 16 that is curved along the arc of a circle in itsconfiguration, this block generally dividing the casing 14 into twochambers, a forward chamber wherein the electro-optical-mechanicalapparatus is housed and a rear chamber wherein the film reels and thepower pack is preferably kept.

With respect to the above said rear chamber, a pair of reels arerotatably mounted in it, one being the film supply reel 17 and the otherbeing the takeup reel 18. The film is designated 19 and is wound on aplurality of rollers 20a-20b as it passes from reel 17 to reel 18.Beneath the reels is the power pack which, in the present instance,comprises one or more batteries 21. As can be seen from the figure, thisrear chamber may be divided into two compartments by a partition 22, thebatteries preferably being mounted in the lower compartment and thereels in the upper compartment.

Referring now to the abovesaid forward chamber, there is mounted thereina turntable 23 and a servomotor 24 for turning the turntable through agearing arrangement 25, the turntable being rotated around a shaft 23awhose axis of rotation is at the domes center of curvature. Rigidly orfixedly mounted on this turntable 23 is a shutter 26 in front of whichis mounted a lens arrangement generally designated 27. As can be seenfrom FIG. 1 A, shutter 26 comprises a frame that is shaped or formedalong a circular arc and which has an aperture in the form of a narrowslot 26a through which the reflected beam of light passes on its way tothe film 19. As can also be seen from FIG. 1 A, rollers 20b and 20c arepositioned at opposite ends of block 16 with the strip of film thatextends 5 between these rollers being interposed between this block 16andshutter 26. The film is held both by block 16 and shutter 26 so thatit 65 curved about the lens center of rotation, with a radius equal tothe focal length. The slot 260 is near the focal plane and parallel tothe above-said axis of rotation, and defines the instantaneous field ofview. Since the shutter is affixed to turntable 23, it obviously moveswith the turntable, with the result that as the turntable rotates, thelight passing through the slot or aperture scans the abovesaid strip offilm for recordation on successive portions of it. This slot and thelens 27 rotate as a unit while the film is being exposed. Completing theoverall shutter mechanism is a split silicon photodetector cell 28 thatis mounted to one side of the shutter aperture and in the proximitythereof.

Extending forwardly from shutter 26 is a hollow cylindrically shapedmember 29 whose rear end is covered or enclosed by the shutter, the slot26a being located where the longitudinal axis of member 29 intersectsthe shutter. As may be noted from the figures under discussion, theinside surface 29a of that portion of the wall of member 29 that liesbetween shutter 26 and lens arrangement 27 is corrugated, thecorrugations being provided to minimize the occurrence of reflectionsfrom the wall that may interfere with or adversely affect the quality ofthe pictures taken. Member 29 extends forwardly beyond lens arrangement27 wherein a prism arrangement 30 is mounted and through which theoutermost portions of the reflected light beam passes for focusing onsilicon cell 28. More particularly, the prism 30 is designed to have arelatively narrow apex angle, 12 for example, a hole 30a being boredthrough the center of the prism to allow the main portion of the beam topass, undeflected, through the center of the lens arrangement 27 and tobe brought to a focus on the film after passing through the slot oraperture. However, the rays that pass through the prism are brought to afocus to one side of the aperture (about 6 to one side) and, therefore,fall on the split silicon 40028. Associated with and coupled toturntable 23 and the apparatus mounted thereon is a motor 31 which,through a gearing arrangement 32, drives a set of rotating chopperblades 33 positioned in front of member 29. Between these rotatingchopper blades 33 and prism 30 are a set of fixed chopper blades 34,these latter blades, in the embodiment shown, being integral with andextending from the front end of member 29. For reasons that will appearmore clearly later, the light beam that passes through prism 30 ischopped by blades 33 so as to produce a 400-cycle pulsed output beam.

A schematic circuit diagram of the servosystem for the described cameraapparatus is shown in FIG. 3 and includes a 400-cycle master oscillator35 connected to a power amplifier 36 that feeds chopper motor 31. Thetwo outputs 28a and 28b of the split photovoltoic cell 28 are connectedto a difference amplifier 37 whose output signal, both as to magnitudeand sense, depends upon the magnitude of the respective signals onoutput lines 280 and 28b and, therefore, on the surface area of cell 28whereat the chopped beam is incident. The difference amplifier isconnected to a power amplifier 38 whose output is fed to one of the twocoils, namely, coil 24a of servomotor 24. The other of these two coils,namely coil 24b is fed by power amplifier 36 through a phase shiftercircuit 39 whose function it is to compensate for any undesirable phaseshifts introduced by circuit components, as is usually the case.

Considering now the operation of the camera, it should be mentioned atthe outset that the function of the servo system and the apparatus itcontrols is to continuously adjust the position of the turntable so thatthe light passing through prism 30 will impinge upon the center ofphotocell 28, that is to say, upon the split thereof. When this occurs,that portion of the beam that passes through prism hole 30a will then beincident upon slot or aperture 26a and will pass through to film 19. Itshould also be mentioned that under such circumstances, the output fromdifference amplifier 37 is reduced to zero which means, in turn, thatservomotor 24 is inactive. On the other hand, if the chopped beam oflight passing through prism 30 impinges on one side or the other of thesplit of cell 28, which means, basically, that the reflected beam is notcentered on aperture 26a, then in that event a signal is developed atthe output of difference amplifier 37. Whether this signal is positiveor negative depends on whether the input to the amplifier is applied online 28a or 28b and it will be recognized that this,

in turn, depends upon which side of the photocell the light impingesupon, as was previously indicated. Needless to say, the signal out ofthe difference amplifier produces an imbalance in coils 24a and 24b,with the result that servo motor 24 is activated to rotate turntable 23in a direction that will restore the beams to their central positionswith respect to both photocell and aperture. Of course, this processgoes on continuously and smoothly as the beam from light source scansthe object to be photographed. Accordingly, as has been shown, thecamera effectively tracks the light beam reflected from the object, withthe result that the camera is continuously pointing towards that portionof the object that is being illuminated as the light beam from the lightsource sweeps across it.

Although a particular arrangement of the invention has been illustratedand described above by way of example, it is not intended that theinvention be limited thereto. Accordingly, the invention should beconsidered to include any and all modifications, alterations orequivalent arrangements falling within the scope of the annexed claims.

Having thus described the invention, what is claimed is:

1. Camera apparatus for photographing an object illuminated by a beam oflight that is being swept across it, said apparatus comprising: a stripof film mounted in the focal plane of the camera apparatus and on whichan image of said object is to be recorded; a rotatably mounted camerasection for focusing the light beam reflected from the object through anaperture therein and onto said film; and means for tracking saidreflected light beam, said means including a device that is receptive ofa portion of said reflected light beam and operable in response theretoto produce an output signal whose magnitude and sense substantiallycorrespond to the shift of said reflected beam from the center of saidaperture, and additional means operable in response to said outputsignal for rotating said camera section so that the illuminated portionof the ob'ect is always within its field of view.

2. he camera apparatus defined in claim 1 wherein said camera sectionincludes a rotatably mounted turntable, a lens arrangement mounted onsaid turntable at the axis of rotation thereof, a shutter frame mountedon said turntable and having an aperture therethrough through which saidreflected light beam is focused on said film, said lens arrangement andsaid shutter frame being fixed to said turntable and rotatabletherewith; and wherein said means includes a device that is receptive ofa portion of said reflected light beam and operable in response theretoto produce an output signal whose magnitude and sense substantiallycorresponds to the shift of said reflected beam from the center of saidaperture.

3. The camera apparatus defined in claim 1 wherein said means includes adevice that is receptive of a portion of said reflected light beam andoperable in response thereto to produce an output signal whose magnitudeand sense substantially corresponds to the shift of said reflected beamfrom the center of said aperture; an oscillator that produces areference signal; and a servomotor coupled to said device and to saidoscillator and operable in response to the signals therefrom to rotatesaid turntable in an amount and in a direction corresponding to thedifferences therebetween.

4. The camera apparatus defined in 1 wherein said camera sectionincludes a rotatably mounted turntable; a lens arrangement mounted onsaid turntable at the axis of rotation thereof, a shutter frame mountedon said turntable and having an aperture therethrough through which saidreflected light beam is focused on said film, said lens arrangement andsaid shutter frame being fixed to said turntable and rotatabletherewith; and wherein said means includes a split photodetector devicemounted on said shutter frame adjacent said aperture therethrough, aprism having a centrally disposed hole therethrough mounted in front ofsaid lens arrangement, said prism being operable to focus the periphealportion of said reflected light bean onto said split photodetectorwhich, in response thereto, produces output signals whose magnitude andsense correspond to the degree said focused beam is not centered on saidsplit, and a servosystem operable in response to said signals to centersaid focused beam on the split of said photodetector.

5. The camera apparatus defined in claim 2 wherein said device includesa split silicon photodetector mounted on said shutter frame adjacentsaid aperture therethrough, a prism having a centrallydisposed holetherethrough mounted in front of said lens arrangement, said prism beingoperable to focus the periphery of said reflected light beam toward saidsplit silicon photodetector, a difference amplifier circuit coupled tothe outputs of said detector, and apparatus for chopping the lightapplied to said prism.

6. The camera apparatus defined in claim 5 wherein said apparatusincludes fixed and rotatable chopper blades mounted in front of saidprism and in the path of the peripheal portion of said reflected beam,and a motor driven to rotate said rotatable chopper blades at apredetermined speed.

1. Camera apparatus for photographing an object illuminated by a beam oflight that is being swept across it, said apparatus comprising: a stripof film mounted in the focal plane of the camera apparatus and on whichan image of said object is to be recorded; a rotatably mounted camerasection for focusing the light beam reflected from the object through anaperture therein and onto said film; and means for tracking saidreflected light beam, said means including a device that is receptive ofa portion of said reflected light beam and operable in response theretoto produce an output signal whose magnitude and sense substantiallycorrespond to the shift of said reflected beam from the center of saidaperture, and additional means operable in response to said outputsignal for rotating said camera section so that the illuminated portionof the object is always within its field of view.
 2. The cameraapparatus defined in claim 1 wherein said camera section includes arotatably mounted turntable, a lens arrangement mounted on saidturntable at the axis of rotation thereof, a shutter frame mounted onsaid turntable and having an aperture therethrough through which saidreflected light beam is focused on said film, said lens arrangement andsaid shutter frame being fixed to said turntable and rotatabletherewith; and wherein said means includes a device that is receptive ofa portion of said reflected light beam and operable in response theretoto produce an output signal whose magnitude and sense substantiallycorresponds to the shift of said reflected beam from the center of saidaperture.
 3. The camera apparatus defined in claim 1 wherein said meansincludes a device that is receptive of a portion of said reflected lightbeam and operable in response thereto to produce an output signal whosemagnitude and sense substantially corresponds to the shift of saidreflected beam from the center of said aperture; an oscillator thatproduces a reference signal; and a servomotor coupled to said device andto said oscillator and operable in response to the signals therefrom torotate said turntable in an amount and in a direction corresponding tothe differences therebetween.
 4. The camera apparatus defined in 1wherein said camera section includes a rotatably mounted turntable; alens arrangement mounted on said turntable at the axis of rotationthereof, a shutter frame mounted on said turntable and having anaperture therethrough through which said reflected light beam is focusedon said film, said lens arrangement and said shutter frame being fixedto said turntable and rotatable therewith; and wherein said meansincludes a split photodetector device mounted on said shutter frameadjacent said aperture therethrough, a prism having a centrally disposedhole therethrough mounted in front of said lens arrangement, said prismbeing operable to focus the peripheal portion of said reflected lightbean onto said split photodetector which, in response thereto, producesoutput signals whose magnitude and sense correspond to the degree saidfocused beam is not centered on said split, and a servosystem operablein response to said signals to center said focused beam on the split ofsaid photodetector.
 5. The camera apparatus defined in claim 2 whereinsaid device includes a split silicon photodeTector mounted on saidshutter frame adjacent said aperture therethrough, a prism having acentrallydisposed hole therethrough mounted in front of said lensarrangement, said prism being operable to focus the periphery of saidreflected light beam toward said split silicon photodetector, adifference amplifier circuit coupled to the outputs of said detector,and apparatus for chopping the light applied to said prism.
 6. Thecamera apparatus defined in claim 5 wherein said apparatus includesfixed and rotatable chopper blades mounted in front of said prism and inthe path of the peripheal portion of said reflected beam, and a motordriven to rotate said rotatable chopper blades at a predetermined speed.